U.S. Autism Rates Rising Fastest for Hispanics, Blacks

"We found that rates among blacks and Hispanics are not only catching up to those of whites -- which have historically been higher -- but surpassing them," said study author Cynthia Nevison, a research scientist at the University of Colorado Boulder.

"These results suggest that additional factors beyond just catch-up may be involved," she added in a university news release.

Among children born between 2007 and 2013, autism rates at ages 3 to 5 rose 73% among Hispanics, 44% among blacks and 25% among whites, the analysis of national data revealed.

In 30 states, rates among blacks were higher than among whites by 2012. In states with high autism rates, 1 in 79 whites, 1 in 68 blacks and 1 in 83 Hispanics born in 2013 was diagnosed with autism by ages 3 to 5.

Some of the increase among minorities is due to more awareness and better detection, but it's likely that other factors are involved, according to the researchers.

"There is no doubt that autism prevalence has increased significantly over the past 10 to 20 years, and based on what we have seen from this larger, more recent dataset it will continue to increase among all race and ethnicity groups in the coming years," said study co-author Walter Zahorodny, an autism researcher and associate professor of pediatrics at Rutgers New Jersey Medical School.

In 2018, the U.S. Centers for Disease Control and Prevention said that about 1 in 59 children of all races have had an autism diagnosis. It reported that rates had increased 15% overall from the previous two-year period, largely due to better outreach and diagnosis among minority groups.

The study authors said their findings challenge that explanation.

"Our data contradict the assertion that these increases are mainly due to better awareness among minority children," Zahorodny said in the release. "If the minority rates are exceeding the white rates, that implies some difference in risk factor, either greater exposure to something in the environment or another trigger."

Known risk factors for autism include: older parent age, immune system challenges during pregnancy, genetic mutations, premature birth and being a twin or multiple.

More research is needed to identify other factors that could be driving the increases, Nevison and Zahorodny said.

The study was published recently in the Journal of Autism and Developmental Disorders.